Brake system control apparatus

ABSTRACT

A non-consideration creating portion creates a non-consideration control command value based on a target value and an actual value of hydraulic pressure of a brake cylinder in a control-target brake system i. A consideration creating portion creates a consideration control command value based on the target value and the actual value of the hydraulic pressure in the control-target brake system i and a target value and an actual value of hydraulic pressure in a comparison-target brake system j. Then, one of the consideration control command value and the non-consideration command value is selected based on an absolute value of a difference in the target value between the control-target brake system i and the comparison-target brake system j, and a combination of a control mode in the control-target brake system i and a control mode in the comparison-target brake system j.

INCORPORATION BY REFERENCE

This is a Division of application Ser. No. 11/251,989 filed Oct. 18,2005, which claims priority to Japanese Patent Application No.2004-307660 filed on Oct. 22, 2004, the disclosures of which are herebyincorporated herein by reference in their entireties.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to a brake system control apparatusincluding plural brake systems, and, more specifically, to control of acontrol actuator of each of the plural brake systems.

2. Description of the Related Art

Japanese Patent Application Publication No. 2004-122974 A discloses abrake system control apparatus that includes plural brake systems eachof which includes a brake and a control actuator that can controlbraking torque applied to a wheel by the brake. The brake system controlapparatus also includes a braking torque control device which creates acontrol command value for the control actuator of each of the pluralbrake systems, and which outputs the control command value to thecontrol actuator. The braking torque control device includes (a) a firstcreating portion that creates a control command value for a controlactuator of a brake system targeted for control (hereinafter, referredto as the “control-target brake system”), which is one of the pluralbrake systems, based a target value of braking torque of a brake of thecontrol-target brake system; (b) a second creating portion that correctsa first control command value, that is, the control command valuecreated by the first creating portion, based on a difference between anactual value of the braking torque applied to the wheel by the brake ofthe control-target brake system and an actual value of braking torque inanother brake system, thereby creating a second control command value;and (c) a control command value selecting portion that selects thesecond control command value, when the actual value of the brakingtorque in the control-target brake system is larger than the actualvalue of the braking torque in the other brake system, and that selectsthe first control command value, when the actual value of the brakingtorque in the control-target brake system is equal to or smaller thanthe actual value of the braking torque in the other brake system.

SUMMARY OF THE INVENTION

It is an object of the invention to make it possible, when at least twocontrol command values are created, to more appropriately select acontrol command value from among the at least two control commandvalues, thereby reducing, if required, a difference in response betweena control-target brake system and each of at least one of the otherbrake systems.

A brake system control apparatus according to a first aspect of theinvention includes plural brake systems each of which includes at leastone brake and a control actuator that can control braking torquegenerated by the at least one brake, the brake system control apparatusincluding a braking torque control device which creates a controlcommand value for the control actuator of each of the plural brakesystems, and which outputs the created control command value to thecontrol actuator. The braking torque control device includes (i) aconsideration creating portion which creates a first control commandvalue for the control actuator of a control-target brake system that isone of the plural brake systems based on information concerning anoperation of the at least one brake in the control-target brake system,and information concerning an operation of the at least one brake ineach of at least one of the other brake systems; (ii) non-considerationcreating portion which creates a second control command value for thecontrol actuator of the control-target brake system based on theinformation concerning the control-target brake system, but not based onthe information concerning each of the at least one of the other brakesystems; and (iii) a control command value selecting portion whichselects one of the first control command value created by theconsideration creating portion and the second control command valuecreated by the non-consideration creating portion based on at least oneof (a) an absolute value of a difference between a target value ofbraking torque in the control-target brake system, and a target value ofbraking torque in each of the at least one of the other brake systems;and (b) a combination of a control mode in the control-target brakesystem and a control mode in each of the at least one of the other brakesystems.

For example, it is not preferable to select the first control commandvalue (consideration control command value) when the absolute value ofthe difference in the target value of the braking torque between thecontrol-target brake system and each of the at least one of the otherbrake-systems is large. When the absolute value of the difference in thetarget value is equal to or larger than a set value, it is consideredthat a situation concerning the control in the control-target brakesystem is different from a situation concerning the control in each ofthe at least one of the other brake systems. Accordingly, it is notpreferable to take the information concerning each of the at least oneof the other brake systems into consideration.

Also, when the control mode in the control-target brake system is anincreasing mode in which the braking torque is increased, and thecontrol mode in each of the at least one of the other brake systems is adecreasing mode in which the braking torque is decreased, the directionsin which the control torque is changed in the control are different fromeach other. Accordingly, it is not preferable to take the informationconcerning each of the at least one of the other brake systems intoconsideration.

As in the case of the first aspect, in the case where the controlcommand value is selected based on the absolute value of the differencein the target value between the control-target brake system and each ofthe at least one of the other brake systems and/or the combination ofthe control modes, if it is not preferable to take the informationconcerning each of the at least one of the other brake systems intoconsideration, the second control command value (non-considerationcontrol command value) is selected. Accordingly, the braking torque canbe controlled based on the state of the control-target brake system. Onthe other hand, when it is preferable to take the information concerningeach of the at least one of the other brake systems into consideration,the first control command value is selected. Accordingly, a differencein response between the control-target brake system and each of the atleast one of the other brake systems can be reduced. Also, simultaneityof the entire brake system control apparatus can be improved.

(2) The selecting portion may select the first control command valuecreated by the consideration creating portion, when the combination ofthe control mode in the control-target brake system and the control modein each of the at least one of the other brake systems is apredetermined combination; and the selecting portion may select thesecond control command value created by the non-consideration creatingportion, when the combination of the control mode in the control-targetbrake system and the control mode in each of the at least one of theother brake systems is not the predetermined combination.

(3) The selecting portion may select the first control command valuecreated by the consideration creating portion, when the control mode inthe control-target brake system and the control mode in each of the atleast one of the other brake systems are the same, and each of both thecontrol mode in the control-target brake system and the control mode ineach of the at least one of the other brake systems is the increasingmode in which the braking torque is increased or the decreasing mode inwhich the braking torque is decreased; and the selecting portion mayselect the second control command value created by the non-considerationcreating portion, when one of the control mode in the control-targetbrake system and the control mode in each of the at least one of theother brake systems is the increasing mode in which the braking torqueis increased, and the other of the control mode in the control-targetbrake system and the control mode in each of the at least one of theother brake systems is the decreasing mode in which the braking torqueis decreased.

The first control command value is selected, when the control mode inthe control-target brake system and the control mode in each of the atleast one of the other brake systems are the same, and each of both ofthe control modes is the increasing mode or the decreasing mode, namely,when the combination of the control modes is a combination of(increasing mode and increasing mode) or a combination of (decreasingmode and decreasing mode). When the control is performed so that thebraking torque in the control-target brake system and the braking torquein each of the at least one of the other brake systems are changed inthe same direction, it is considered that the level of response in thecontrol-target brake system and the level of response in each of the atleast one of the other brake systems are required to be the same.Accordingly, it is appropriate to select the first control commandvalue.

In contrast to this, the second control command value is selected, whenthe combination of the control mode in the control-target brake systemand the control mode in each of the at least one of the other brakesystems is a combination of the increasing mode and the decreasing mode,namely, a combination of (increasing mode and decreasing mode) or acombination of (decreasing mode and increasing mode). In these cases,the directions of the control of the braking torque are different.Accordingly, the levels of response are not always required to be thesame. Therefore, it is appropriate to select the second control commandvalue in this case.

The first control command value may be selected, when the control modein the control-target brake system is one of the increasing mode and thedecreasing mode, and the control mode in each of the at least one of theother brake systems is a maintaining mode in which the braking torque ismaintained, namely, when the combination of the control modes is acombination of (increasing mode and maintaining mode) or a combinationof (decreasing mode and maintaining mode). When the control mode in eachof the at least one of the other brake systems is the maintaining mode,a delay in control (hereinafter, referred to as a “control delay”) inthe control-target brake system may be larger than a control delay ineach of the at least one of the other brake systems. Accordingly, it maybe preferable to select the first control command value.

(4) The selecting portion may select the second control command valuecreated by the non-consideration creating portion, when the absolutevalue of the difference in the target value of the braking torquebetween the control-target brake system and each of the at least one ofthe other brake systems is equal to or larger than a set value; and theselecting portion may select the first control command value created bythe consideration creating portion, when the absolute value of thedifference in the target value of the braking torque between thecontrol-target brake system and each of the at least one of the otherbrake systems is smaller than the set value.

When the target value in the control-target brake system is differentfrom the target value in each of the at least one of the other brakesystems by a large amount, the directions in which the braking forcechange may different from each other. Also, the same level of responsemay not be required. Accordingly, in these cases, it is preferable notto select the first control command value.

(5) The selecting portion may select the second control command valuecreated by the non-consideration creating portion, if the absolute valueof the difference in the target value of the braking torque between thecontrol-target brake system and each of the at least one of the otherbrake systems is equal to or larger than the set value, even when thecombination of the control mode in the control-target brake system andthe control mode in each of the at least one of the other brake systemsis the predetermined combination.

(6) The selecting portion may select the second control command valuecreated by the non-consideration creating portion, if the combination ofthe control mode in the control-target brake system and the control modein each of the at least one of the other brake systems is not thepredetermined combination, even when the absolute value of thedifference in the target value of the braking torque between thecontrol-target brake system and each of the at least one of the otherbrake systems is smaller than the set value.

Even when the combination of the control mode in the control-targetbrake system and the control mode in each of the at least one of theother brake systems is the predetermined combination, if the absolutevalue of the difference in the target value is equal to or larger thanthe set value, it is preferable to select the second control commandvalue. For example, even when each of both of the control modes is theincreasing mode, or each of both of the control modes is the decreasingmode, if the absolute value of the difference in the target value isequal to or larger than the set value, the same level of response maynot be required.

Also, even when the absolute value of the difference in the target valuebetween the control-target brake system and each of the at least one ofthe other brake systems is smaller than the set value, if thecombination of the control modes is the combination of (increasing modeand the decreasing mode), it is preferable to select the second controlcommand value, since the directions in which the braking torque ischanged are different from each other.

As described so far, it is preferable to select the first controlcommand value, when the absolute value of the difference in the targetvalue between the control-target brake system and each of the at leastone of the other brake systems is smaller than the set value, and thecombination of the control modes is the predetermined combination.

(7) The selecting portion may select the second control command valuecreated by the non-consideration creating portion, when an absolutevalue of a difference between an absolute value of a deviation of anactual value from the target value of the braking torque in thecontrol-target brake system, and an absolute value of a deviation of anactual value from the target value of the braking torque in each of theat least one of the other brake systems is equal to or larger than a setvalue; and the selecting portion may select the first control commandvalue created by the consideration creating portion, when the absolutevalue of the difference between the absolute value of the deviation ofthe actual value from the target value of the braking torque in thecontrol-target brake system, and the absolute value of the deviation ofthe actual value from the target value of the braking torque in each ofthe at least one of the other brake systems is smaller than the setvalue.

When the absolute value (|LΔeij|) of the difference (LΔeij=|Δei|−|Δej|)between the absolute value of the deviation (Δei) in the control-targetbrake system “i” and the absolute value of the deviation (Δej) in eachof the at least one of the other brake systems “j” is equal to or largerthan the set value, a difference in a control delay (a difference inresponse) between the control-target brake system “i” and each of the atleast one of the other brake systems “j” is large.

When the difference (|ei|−|Δej|) in the absolute value of the deviationis a positive value, the control delay in the control-target brakesystem “i” is larger than the control delay in each of the at least oneof the other brake systems “j”. A difference in response (difference incontrol delay) when the absolute value (|LΔeij|) of the difference inthe absolute value of the deviation is large is larger than thedifference in response when the absolute value (|LΔeij|) is small.

Similarly, when the difference (|Δei|−|Δej|) in the absolute value ofthe deviation is a negative value, the control in the control-targetbrake system “i” is advanced as compared with the control in each of theat least one of the other brake systems “j”, and the difference inresponse when the absolute value (|LΔeij|) of the difference is large islarger than the difference in response when the absolute value (|LΔeij|)of the difference is small.

Accordingly, when the absolute value (|LΔeij|) of the difference in theabsolute value of the deviation is equal to or larger than the setvalue, it is not preferable to take the information concerning each ofthe at least one of the other brake systems into consideration.Therefore, it is appropriate to select the second control command value.On the other hand, when the absolute value (|LΔeij|) of the differencein the absolute value of the deviation is smaller than the set value, itis preferable to take the information concerning each of the at leastone of the other brake systems into consideration. Therefore, it isappropriate to select the first control command value.

(8) The braking torque control device may perform feedback control basedon the deviation of the actual value from the target value of thebraking torque in each of the plural brake systems.

According to this aspect, the control actuator is controlled based onthe difference between the target value and the actual value, the actualvalue is fed back, and the control command value is created such thatthe actual value comes closer to the target value. The control commandvalue is created based on the target value and the actual value of thebraking torque in at least the control-target brake system, regardlessof whether the control command value is creased by the considerationcreating portion or the non-consideration creating portion.

(9) The consideration creating portion may create the control commandvalue based on the target value and the actual value of the brakingtorque in the control-target brake system, and the target value and theactual value of the braking torque in each of the at least one of theother brake systems.

The feedback control is performed based on the target value and theactual value in the control-target brake system. Accordingly, it isappropriate to create the first control command value based on thetarget value and the actual value of the braking torque in thecontrol-target brake system, and the target value and the actual valueof the braking torque in each of the at least one of the other brakesystems.

In the feed-forward control, when the non-consideration creating portioncreates the control command value based on the target value, theconsideration creating portion may create the control command valuebased on the target value in the control-target brake system, the actualvalue in the control-target brake system, and the actual value in eachof the at least one of the other brake systems.

(10) The consideration creating portion may create the first controlcommand value based on the deviation of the actual value from the targetvalue of the braking torque in the control-target brake system, and thedeviation of the actual value from the target value of the brakingtorque in each of the at least one of the other brake systems.

The control mode for the braking torque (whether the control forincreasing the braking torque or the control for decreasing the brakingtorque is performed), and a degree of the control delay (level ofresponse) can be obtained based on whether the deviation is a positivevalue or a negative value, and the absolute value of the deviation.Accordingly, the control mode of the braking torque in the brake systemand the degree of the control delay can be obtained based on thedeviation in each of the at least one of the other brake systems. If thecontrol command value is created in consideration of the deviation ineach of the at least one of the other brake systems and the deviation inthe control-target brake system, the control command value can becreated based on the degree of the control delay and the combination ofthe control modes. Accordingly, the control actuators can be controlledsuch that the same level of response can be obtained.

(11) The consideration creating portion may correct the second controlcommand value created by the non-consideration creating portion, basedon the target value and the actual value in each of the at least one ofthe other brake systems and the target value and the actual value in thecontrol-target brake system.

(12) The consideration creating portion may create the control commandvalue by correcting the control command value created by thenon-consideration creating portion, based on the deviation of the actualvalue from the target value of the braking torque in the control-targetbrake system and the deviation of the actual value from the target valueof the braking torque in each of the at least one of the other brakesystems.

(13) The consideration creating portion may set a correction value basedon a difference between the absolute value of the deviation of theactual value from the target value of the braking torque in thecontrol-target brake system, and the absolute value of the deviation ofthe actual value from the target value of the braking torque in each ofthe at least one of the other brake systems.

As mentioned above, whether the control delay in the control-targetbrake system is larger than the control delay in each of the at leastone of the other brake systems, the degree of the control delay in eachof the control-target brake system and the at least one of the otherbrake systems, and the like can be obtained based on whether the valueLΔeij obtained by subtracting the absolute value of the deviation ineach of the at least one of the other brake systems “j” from theabsolute value of the deviation in the control-target brake system “i”is a positive value or a negative value, and based on the absolute valueof the value LΔeij. Accordingly, it is appropriate to set the correctionvalue based on the difference LΔeij in the absolute value of thedeviation.

For example, when the difference LΔeij in the absolute value of thedeviation is a positive value, the control command value is correctedsuch that a rate of change in the braking torque becomes high. On theother hand, when the difference LΔeij in the absolute value of thedeviation is a negative value, the control command value is correctedsuch that the rate of change in the braking torque becomes low.

More specifically, in the case where the rate of change in the brakingtorque when the control command value is large is higher than the rateof change in the braking torque when the control command value is small,when the consideration creating portion creates the first controlcommand value by adding the correction value to the second controlcommand value, if the difference LΔeij in the absolute value of thedeviation is a positive value, the correction value is set to a positivevalue, and the positive correction value when the absolute value |LΔeij|of the difference in the absolute value of the deviation is large can bemade larger than the positive correction value when the absolute value|LΔeij| of the difference in the absolute value of the deviation issmall. Thus, the control delay in the control-target brake system, whichis larger than the control delay in each of the at least one of theother brake systems can be reduced, and the difference in response canbe reduced. On the other hadn, when the difference LΔeij in the absolutevalue of the deviation is a negative value, the correction value is setto a negative value, and the negative correction value when the absolutevalue |LΔeij| of the difference is large can be made smaller than thenegative correction value when the absolute value |LΔeij| of thedifference is small. Thus, the first control command value can set to asmall value, and the degree of advance of the control in thecontrol-target brake system with respect to each of the at least one ofthe other brake systems can be reduced.

In the case where the consideration creating portion corrects a gain Kthat is used when the first control command value is created (K=α×K,when the gain is corrected by being multiplied by a gain correctioncoefficient α. When the gain correction coefficient is “1”, the gain isnot corrected, namely, when the second control command value isobtained), when the difference LΔeij in the absolute value of thedeviation is a positive value, the gain correction coefficient α is setto a value equal to or larger than “1”, and the absolute value of thegain correction coefficient when the absolute value |LΔeij| of thedifference is large is made larger than the absolute value of the gaincorrection coefficient when the absolute value |LΔeij| of the differenceis small. Also, when the difference LΔeij of the absolute value of thedeviation is a negative value, the gain correction coefficient α is setto a value smaller than “1”, and the gain correction coefficient α whenthe absolute value |LΔeij| of the difference is large can be madesmaller than the gain correction coefficient α when the absolute value|LΔeij| of the difference is small, in a range where the gain correctioncoefficient α is larger than “0”.

(14) The consideration creating portion may create the first controlcommand value for the control-target brake system based on theinformation concerning the control-target brake system and theinformation concerning the brake system whose level of response isrequired to the same as that of the control-target brake system.

When the brake system control apparatus includes plural brake systems,the information concerning any brake system(s) other than thecontrol-target brake system may be taken into consideration. However, itis preferable that the information concerning the brake system whoselevel of response is required to be the same as that of thecontrol-target brake system be taken into consideration, among the otherbrake systems. For example, when the absolute value of the difference inthe target value is equal to or smaller than the set value, when thecombination of the control modes is the predetermined combination, orthe like, it can be considered that the same level of response isrequired.

Also, the brake system whose level of response is required to be thesame as that of the control-target brake system may be decided based ona structure of a vehicle. For example, when the normal braking operationis performed, namely, when the braking torque in each of the brakesystems is controlled such that the braking torque required by thedriver can be obtained, the brake systems corresponding to right andleft wheels on each of the front wheel side and the rear wheel side arethe brake systems whose levels of response are required to be the same.

(15) The consideration creating portion may create the first controlcommand value based on the information concerning the control-targetbrake system and the information concerning the brake system includingthe brake that suppresses rotation of the wheel which is on an oppositeside, in a right-and-left direction, of the wheel whose rotation issuppressed by the control-target brake system.

(16) The brake may be a hydraulic brake that applies hydraulic brakingtorque to a brake rotational body that can rotate together with thewheel by pressing a friction member to the brake rotational body due tohydraulic pressure of a brake cylinder, thereby suppressing rotation ofthe wheel, and the control actuator may include at least oneelectromagnetic control valve that can control the hydraulic pressure ofat least one brake cylinder. The braking torque control device mayinclude a hydraulic pressure control device that controls the hydraulicpressure of each of the at least one brake cylinder by creating thecontrol command value corresponding to an electric current supplied tothe electromagnetic control valve, and outputting the control commandvalue to the electromagnetic control valve.

In the brake system control apparatus according to the above-mentionedaspect, the electromagnetic control valve serving as the controlactuator is controlled, and the control command value indicating theelectric current supplied to the electromagnetic control valve iscreated. One brake is provided with one electromagnetic control valve,or two electromagnetic control valves. The control actuator includes apressure increasing control valve and a pressure decreasing controlvalve. In the increasing mode in which the hydraulic pressure of thebrake cylinder is increased, the electric current supplied to thepressure increasing control valve is controlled. In the decreasing modein which the hydraulic pressure of the brake cylinder is decreased, theelectric current supplied to the pressure decreasing control valve iscontrolled. In this case, when the control mode is decided, theelectromagnetic control valve targeted for the control is decided.

Also, the electromagnetic control valve may be an electromagneticopen/close valve that is opened/closed by ON/OFF control of the supplyelectric current, or may be a linear control valve. In the case of thelinear control valve, an amount of electric current supplied to thelinear control valve is continuously controlled, and the linear controlvalve permits hydraulic fluid, whose amount corresponds to the amount ofsupply electric current, to flow therethrough. When the electromagneticcontrol valve is the electromagnetic open/close valve, the controlcommand value corresponding to the ON/OFF state of the supply electriccurrent, a duty control ratio, and the like is created. When theelectromagnetic control valve is the linear control valve, the controlcommand value corresponding to the amount of supply electric current iscreated.

(17) The electromagnetic control valve may permit the hydraulic fluid toflow therethrough at an opening amount that is decided based on at leastthe electric current supplied to the electromagnetic control valve, andthe consideration creating portion may create the first control commandvalue indicating the supply electric current such that the difference inresponse between the control-target brake system and each of the atleast one of the other brake systems is reduced.

The electromagnetic control valve may be configured such that theopening amount when the supply electric current is large is larger thanthe opening amount when the supply electric current is small.Alternatively, the electromagnetic control valve may be configured suchthat the opening amount when the supply electric current is large issmaller than the opening amount when the supply electric current issmall. In either of these cases, the amount of hydraulic fluid flowingin/out of the brake cylinder when the opening amount is large can bemade larger than the amount of hydraulic fluid flowing in/out of thebrake cylinder when the opening amount is small. Thus, the hydraulicpressure of the brake cylinder can be made closer to the targethydraulic pressure promptly.

(18) The electromagnetic control valve may include a seating valveincluding a valve element, a valve seat, and a spring; and anelectromagnetic driving force applying device including a solenoid. Therelative position of the valve element with respect to the valve seat isset based on a relationship among electromagnetic driving force appliedby the electromagnetic driving force applying device, force applied bythe spring, and differential pressure applying force that acts accordingto a pressure difference between the upstream side and the downstreamside of the electromagnetic control valve.

When the spring is provided so as to apply force such that the valveelement contacts the valve seat, the electromagnetic control valve is anormally closed valve. When the spring is provided so as to apply forcesuch that the valve element moves away from the valve seat, theelectromagnetic control valve is a normally open valve.

(19) A brake system control apparatus according to a second aspect ofthe invention includes plural brake systems each of which includes atleast one brake and a control actuator that can control braking torquegenerated by the at least one brake, the brake system control apparatusincluding a braking torque control device which creates a controlcommand value for the control actuator of each of the plural brakesystems, and which outputs the created control command value to thecontrol actuator. The braking torque control device includes aconsideration creating portion that creates the control command valuefor the control actuator of a control-target brake system that is one ofthe plural brake systems, based on an actual value and a target value ofbraking torque in the control-target brake system and an actual valueand a target value of braking torque in each of at least one of theother brake systems.

According to the second aspect, the control command value for thecontrol-target brake system is created based on the target value and theactual value of the braking torque in the control-target brake system,and the target value and the actual value of the braking torque in eachof at least one of the other brake systems.

Since the control command value is created based on the target value andthe actual value of the braking torque in each of the at least one ofthe other brake systems (the consideration-target brake system) and thetarget value and the actual value in the control-target command value,it becomes possible to take not only the deviation in the control-targetbrake system but also the deviation in the consideration-target brakesystem into consideration. Accordingly, the level of response in thecontrol-target brake system and the level of response in each of the atleast one of the other brake systems can the same.

Namely, whether the information concerning each of the at least one ofthe other brake systems is taken into consideration is determined basedon the target value and the actual value in each of the at least one ofthe other brake systems and the target value and the actual value in thecontrol-target brake system, it becomes possible to accurately determinewhether the information concerning each of the at least one of the otherbrake systems should be taken into consideration.

(20) A brake system control apparatus according to a third aspect of theinvention includes a consideration creating portion which creates acontrol command value for a control actuator of a control-target brakesystem that is one of the plural brake systems based on at least atarget value of braking torque in the control-target brake system; anabsolute value of a deviation of an actual value from the target valueof the braking torque in the control-target brake system; and anabsolute value of a deviation of an actual value from a target value ofthe braking torque in each of at least one of the other brake systems.

(21) In a brake system control apparatus according to a fourth aspect ofthe invention, the braking torque control device includes a firstcreating portion which creates a control command value for a controlactuator of a control-target brake system that is one of the pluralbrake systems based on at least a target value of braking torque in thecontrol-target brake system; a second creating portion which creates asecond control command value by correcting the first control commandvalue created by the first creating portion based on the value obtainedby subtracting an absolute value of a deviation of an actual value froma target value of braking torque in each of at least one of the otherbrake systems from an absolute value of a deviation of an actual valuefrom the target value of the braking torque in the control-target brakesystem; and a control command value selecting portion which selects oneof the first control command value and the second control command valuebased on a state of the brake system control apparatus.

(22) A brake system control apparatus according to a fifth aspect of theinvention includes a consideration creating portion which creates afirst control command value for a control actuator of a control-targetbrake system that is one of the plural brake systems based oninformation concerning an operation of the at least one brake in thecontrol-target brake system and information concerning each of at leastone of the other brake systems; a non-consideration creating portionwhich creates a second control command value for the control actuator ofthe control-target brake system based on the information concerning thecontrol-target brake system, but not based on the information concerningeach of the at least one of the other brake systems; and a controlcommand value selecting portion which selects one of the first controlcommand value created by the consideration creating portion and thesecond control command value created by the non-consideration creatingportion based on a target value of braking torque in the control-targetbrake system and a target value in each of the at least one of the otherbrake systems.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and further objects, features and advantages of theinvention will become apparent from the following description ofpreferred embodiments with reference to the accompanying drawings,wherein like numerals are used to represent like elements and wherein:

FIG. 1 is a circuit diagram showing a hydraulic brake apparatus that isa brake system control apparatus according to an embodiment of theinvention;

FIG. 2 is a cross sectional view schematically showing a normally closedvalve included in an individual hydraulic pressure control valve deviceprovided in the hydraulic brake apparatus;

FIG. 3 is a cross sectional view schematically showing a normally openvalve included in the individual hydraulic pressure control valvedevice;

FIGS. 4A and 4B are a flowchart showing a control command value creatingprogram stored in a storing portion of a brake ECU of the hydraulicbrake apparatus;

FIG. 5 is a graph conceptually showing a control threshold value storedin the storing portion of the brake ECU;

FIG. 6 is a block diagram showing a structure of the brake ECU;

FIG. 7 is a flowchart showing another control command value creatingprogram stored in the storing portion of the brake ECU; and

FIG. 8 is a flowchart showing a part of the control command valuecreating program.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Hereafter, a brake system control apparatus according to an embodimentof the invention will be described in detail with reference toaccompanying drawings.

A brake system control apparatus shown in FIG. 1 includes a brake pedal10 serving as a brake operating member; a master cylinder 12 includingtwo compressing chambers; a pump device 14 serving as a hydraulicpressure source; and hydraulic brakes 16, 17, 18, and 19 that areprovided for a left front wheel, a right front wheel, a left rear wheel,and a right rear wheel, respectively.

The hydraulic brakes 16, 17, 18, and 19 include brake cylinders 20, 21,22, and 23, respectively. The hydraulic brakes 16, 17, 18, and 19 areoperated by the hydraulic pressures of the brake cylinders 20, 21, 22,and 23, respectively, thereby applying braking torque to the respectivewheels.

The master cylinder 12 includes two compressing pistons. When a driveroperates the brake pedal 10, hydraulic pressure corresponding to thebrake pedal operation force is generated in each of hydraulic chamberspositioned ahead of the two respective compressing pistons. The twocompressing chambers of the master cylinder 12 are connected to thebrake cylinder 20 for the left front wheel and the brake cylinder 21 forthe right front wheel through master passages 26 and 27, respectively.Master shut-off valves 29 and 30 are provided in the master passages 26and 27, respectively. Each of the master shut-off valves 29 and 30 is anormally open electromagnetic open/close valve.

The four brake cylinders 20, 21, 22, and 23 are connected to the pumpdevice 14 through a pump passage 36. While the brake cylinders 20 and 21are shut off from the master cylinder 12, hydraulic pressure is suppliedfrom the pump device 14 to the brake cylinders 20, 21, 22, and 23,whereby the hydraulic brakes 16, 17, 18, and 19 are operated. Thehydraulic pressure of each of the brake cylinders 20, 21, 22, and 23 iscontrolled by a hydraulic pressure control valve device 38.

The pump device 14 includes a pump motor 58 that drives a pump 56. Amaster reservoir 62 is connected to an inlet side of the pump 56 throughan intake passage 60, and an accumulator 64 is connected to an outletside of the pump 56. A hydraulic fluid in the reservoir 62 is pumped upby the pump 56, and supplied to the accumulator 64. Then, the hydraulicfluid is stored in the accumulator 64 while being compressed.

The outlet side and the inlet side of the pump 56 are connected by arelief passage 66. A relief valve 68 is provided in the relief passage66. The relief valve 68 is opened when the hydraulic pressure on theaccumulator side, that is, the high pressure side, exceeds a setpressure.

The hydraulic pressure control valve device 38 includes individualhydraulic pressure control valve devices 70, 71, 72, and 73 provided forthe brake cylinders 20, 21, 22, and 23, respectively. The individualhydraulic pressure control valve devices 70, 71, 72, and 73 includepressure increasing linear valves 80, 81, 82, and 83, and pressuredecreasing linear valves 90, 91, 92, and 93, respectively. The pressureincreasing linear valves 80, 81, 82, and 83 are provided in the pumppassage 36, and serve as electromagnetic pressure increasing controlvalves. The pressure decreasing linear valves 90, 91, 92, and 93 areprovided in a pressure decreasing passage 86 which connects the brakecylinders 20, 21, 22, and 23 to the reservoir 62, and serve aselectromagnetic pressure decreasing control valves. The pressures of thebrake cylinders 20, 21, 22 and 23 can be controlled independently ofeach other by controlling the pressure increasing linear valves 80, 81,82, and 83 and the pressure decreasing linear valves 90, 91, 92, and 93.

The pressure increasing linear valves 80, 81, 82 and 83 provided for theleft front wheel, the right front wheel, the left rear wheel and theright rear wheel, respectively, and the pressure decreasing linearvalves 90 and 91 provided for the left front wheel and the right frontwheel, respectively, are normally closed valves, namely, these valvesare closed when an electric current is not supplied to a coils 100. Thepressure decreasing linear valves 92 and 93 corresponding to the leftrear wheel and the right rear wheel, respectively, are normally openvalves, that is, these valves are open when an electric current is notsupplied to a coil 102.

FIG. 2 shows each of the pressure increasing linear valves 80, 81, 82,and 83 and the pressure decreasing linear valves 90 and 91, which arenormally closed valves. Each of the pressure increasing linear valves80, 81, 82, and 83 and the pressure decreasing linear valves 90 and 92includes a solenoid 104 including a coil 100, a plunger 103 and thelike; and a seating valve 110 including a valve element 105, a valveseat 106, a spring 108 which applies force in a direction in which thevalve element 105 contacts the valve seat 106, and the like.

Then an electric current is not supplied to the coil 100, the valveelement 105 contacts the valve seat 106 due to force Fs of the spring108, namely, the valve is closed. When an electric current is suppliedto the coil 100, electromagnetic driving force Fd corresponding to thesupplied electric current is applied to the plunger 103, and acts in adirection in which the valve element 105 moves away from the valve seat106. Also, differential pressure acting force Fp corresponding to adifference in the pressure between the upstream side and the downstreamside of the valve acts in the direction in which the valve element 105moves away from the valve seat 106. The relative position of the valveelement 105 with respect to the valve seat 106 is decided based on arelationship between the electromagnetic driving force Fd and thedifferential pressure acting force Fp, and the force Fs of the spring.Hydraulic fluid whose amount corresponds to a valve opening amountdetermined based on the electromagnetic driving force Fd is allowed toflow through the valve.

FIG. 3 shows each of the pressure decreasing linear valves 92 and 93which are the normally open valves. Each of the pressure decreasinglinear valves 92 and 93 includes a solenoid 112 including a coil 102, aplunger 111 and the like; and a seating valve 120 including a valveelement 114, a valve seat 116, a spring 118 which applies force suchthat the valve element 114 moves away from the valve seat 116, and thelike. The pressure decreasing linear valve 92 is provided between thebrake cylinder 22 and the reservoir 62 in a state where the differentialpressure acting force Fp corresponding to a difference in pressurebetween the brake cylinder 22 and the reservoir 62 is applied to thevalve elements 114. Similarly, the pressure decreasing linear valve 93is provided between the brake cylinder 23 and the reservoir 62 in astate where the differential pressure acting force Fp corresponding to adifference in pressure between the brake cylinder 23 and the reservoir62 is applied to the valve elements 114. While an electric current isnot supplied to the coil 102, the valve element 114 is kept away fromthe valve seat 116 due to the differential pressure acting force Fp andthe force Fs of the spring 118, namely, the valve is open. When anelectric current is supplied to the coil 102, the electromagnetic forceFd corresponding to the electric current acts in the direction in whichthe valve element 114 contacts the valve seat 116. The relative positionof the valve element 114 with respect to the valve seat 116 is decidedbased on a relationship between the force Fs of the spring 118 and thedifferential pressure acting force Fp, and the electromagnetic drivingforce Fd.

A stroke simulator device 150 is provided in the master passage 26. Thestroke simulator device 150 includes a stroke simulator 152 and anormally closed simulator open/close valve 154. The simulator open/closevalve 154 is opened/closed, whereby communication between the strokesimulator 152 and the master cylinder 12 is permitted/interrupted. Inthe embodiment, the state where the hydraulic brakes 16, 17, 18, and 19are operated by the hydraulic fluid supplied from the pump device 14 isan open state; and a state where the hydraulic brakes 16, 18, 18, and 19are operated by the hydraulic fluid supplied from the master cylinder 12is a closed state.

As shown in FIG. 1, the brake system control apparatus is controlledaccording to a command transmitted from a brake ECU 200. The brake ECU200 is formed mainly of a computer, and includes an executing portion202, a storing portion 204, an input/output portion 206, and the like.The input/output portion 206 is connected to a stroke sensor 210, amaster pressure sensor 214, a brake hydraulic pressure sensor 216, awheel speed sensor 218, a hydraulic pressure source hydraulic sensor220, and the like. The input/output portion 206 is connected, through aswitch circuit (not shown), to the coil 100 of each of the pressureincreasing linear valves 80, 81, 82, and 83, the coil 100 of each of thepressure decreasing linear valves 90 and 91, the coil 102 of each of thepressure decreasing linear valves 92 and 93, a coil of each of themaster shut-off valves 29 and 30, and a coil of the simulator controlvalve 154. The input/output portion 206 is also connected to a pumpmotor 58 through a drive circuit.

The storing portion 204 stores a control command value creating program,which is shown in a flowchart in FIGS. 4A and 4B, and the like.

In the embodiment, brake systems 230, 231, 232, and 233 are formedmainly of the brake cylinders 20, 21, 22 and 23, and the individualhydraulic pressure control valve devices 70, 71, 72, and 73,respectively. The control actuators are formed of the individual controlvalve devices 70, 71, 72, and 73, respectively. The control actuatorsrespectively include the pressure increasing control valves 80, 81, 82,and 83, and the pressure decreasing control valves 90, 91, 92, and 93.

These pressure increasing control valves 80, 81, 82, and 83, and thepressure, decreasing control valves 90, 91, 92, and 93 are controlled ina feedback manner. The brake ECU 200 creates a control command valuesfor the brake systems 230, 231, 232, and 233 based on deviations ofactual values from target values of the hydraulic pressures of the brakecylinders 20, 21, 22, and 23, and outputs the control command values tothe brake systems 230, 231, 232, and 233, respectively. Each of thecontrol command values for the brake systems 230 and 231 indicates anamount of electric current supplied to the 100 such that the actualvalue comes close to the target value. Each of the control commandvalues for the brake systems 232 and 233 indicates an electric currentsupplied to the coil 100 and an electric current supplied to the coil102 such that the actual value comes close to the target value.

The target value of the hydraulic pressure of each of the brakecylinders 20, 21, 22, and 23 is decided based on the operating state ofthe brake pedal 10 achieved by the driver, when the braking operation isperformed normally. The required braking force is calculated based on atleast one of an operation stroke and operation force (corresponding tomaster pressure) of the brake pedal 10, and the target value of thehydraulic pressure of each of the brake cylinder 20, 21, 22, and 23 ofthe respective wheels is decided such that the required braking forcecan be obtained. In the embodiment, the target value of the hydraulicpressure braking torque corresponds to the target value of the hydraulicpressure of the brake cylinder. The target values of the hydraulicpressures of the brake cylinders 20, 21, 22, and 23 of the respectivewheels may be equal to each other. Alternatively, the target value ofthe hydraulic pressure of the brake cylinder 20 of the left front wheeland the target value of the hydraulic pressure of the brake cylinder 21of the right front wheel may be equal to each other, and the targetvalue of the hydraulic pressure of the brake cylinder 22 of the leftrear wheel and the target value of the hydraulic pressure of the brakecylinder 23 of the right rear wheel may be equal to each other, and thetarget value for each of the right and left front wheels and the targetvalue for each of the right and left rear wheels may be set to valuesalong a front and rear braking force distribution line.

In anti-lock control and vehicle stability control, the target values ofthe hydraulic pressures of the brake cylinders 20, 21, 22, and 23 of therespective wheels are individually decided such that states of a brakingslip and a lateral slip become appropriate for a friction coefficient ofa road surface.

In the embodiment, information indicating a supply electric current as acontrol command value is created and output for each of the four brakesystems 230, 231, 232, and 233. In some cases, the control command valueis created based on the target value and the actual value of thehydraulic pressure of the brake cylinder in the control-target brakesystem. In the other cases, the control command value is created basedon the target value and the actual value of the hydraulic pressure ofthe brake cylinder in the control-target brake system, and the targetvalue and the actual value of the hydraulic pressure of the brakecylinder in another brake system. The control command value createdbased on the target value and the actual value in the control-targetbrake system will be referred to as a non-consideration control commandvalue (hereinafter, referred to as a second control command value), andthe control command value created based on the target value and theactual value in the control-target brake system and the target value andthe actual value in the other brake system will be referred to as aconsideration control command value (hereinafter, referred to as a firstcontrol command value).

Then an absolute value of a difference between the target value in thecontrol-target brake system and the target value in the other brakesystem is equal to or smaller than a set value, and a control mode inthe control-target brake system and a control mode in the other brakesystem are the same and each of both of these control modes is thepressure increasing mode or the pressure decreasing mode, namely, acombination (MODEi, MODEj) of the control modes in the two brake systemsis a combination of (pressure increasing mode and pressure increasingmode) or a combination of (pressure decreasing mode and pressuredecreasing mode), the first control command value is created. On theother hand, when the absolute value of the difference between the targetvalue in the control-target brake system and the target value in theother brake system is larger than the set value, when the control modesin these brake systems do not match each other, or when each of both ofthe control modes is the maintaining mode, namely, the combination ofthe control modes (MODEi, MODEj) is a combination of (pressureincreasing mode and pressure decreasing mode), a combination of(pressure increasing mode and pressure decreasing mode), a combinationof (pressure increasing mode and maintaining mode), a combination of(pressure decreasing mode and maintaining mode), or a combination of(maintaining mode and maintaining mode), the second control commandvalue is created.

As shown in FIG. 5, when the deviation of the actual value from thetarget value (Δe=Pref−Pwc) becomes smaller than a pressure decreasethreshold value, the control mode is set to the pressure decreasingmode. The control mode is maintained at the pressure decreasing modeuntil the deviation exceeds a pressure decrease maintaining thresholdvalue. When the deviation exceeds the pressure decrease maintainingthreshold value, the control modes is set to the maintaining mode. Whenthe deviation exceeds a pressure increase threshold value, the controlmode is changed from the maintaining mode to the pressure increasingmode. When the deviation becomes smaller than a pressure increasemaintaining threshold value, the control mode is changed from thepressure increasing mode to the maintaining mode. Each of the pressuredecrease threshold value, the pressure decrease maintaining thresholdvalue, the pressure increase maintaining threshold value, and thepressure increase threshold value is set in advance, and stored in thestoring portion 204.

The control-target brake system is one of the plural brake systems 230,231, 232, and 233. When the control-target brake system is the brakesystem 230 for the left front wheel, the other brake system is the brakesystem 231 for the right front wheel. When the control-target brakesystem is the brake system 232 for the left rear wheel, the other brakesystem is the brake system 233 for the right rear wheel. When thecontrol-target brake system is the brake system for one of the right andleft front wheels, the brake system for the other of the right and leftfront wheels is the other brake system. When the control-target brakesystem is the brake system for one of the right and left rear wheels,the brake system for the other of the right and left rear wheels is theother brake system. In each of the front wheel side and the rear wheelside, the same level of response is required in the brake systems forthe right and left wheels.

Hereafter, a description will be made concerning the case where one ofthe brake system 230 for the left front wheel and the brake system 231for right front wheel is the control-target brake system, and the otherof the brake systems 230 and 231 is the other brake system. In the casewhere the control command value indicating the supply electric currentis large, each of the pressure increasing control valves 80 and 81, andthe pressure decreasing control valves 90 and 91 included in theindividual hydraulic pressure control valve devices 70 and 71corresponding to the brake cylinder 20 for the left front wheel 20 andthe brake cylinder 21 for the right front wheel, respectively, permits alarge amount of hydraulic fluid to flow therethrough, as compared withthe case where the control command value is small. Hereafter, the otherbrake system will be referred to as a comparison-target brake system.When the first control command value is created in consideration of theinformation concerning the comparison-target brake system, thecomparison-target brake system is a consideration-target brake system.

A second control command value PIDIi is created based on a deviation Δeiin a control-target brake system i, a derivative value of the deviation(dPrefi/dt−dPwci/dt), and an integral value Σei of the deviation,according to an equation, PIDIi=KP (Δei+CP)+KD(dPrefi/dt−dPwci/dt+CD)+KI (ΣΔei+CI)+Ci. Here, each of KP, KI, and KD isa gain, and each of CP, CD, CI, and Ci is a constant. Since the secondcontrol command value is formed of a proportional term, a derivativeterm and an integral term, the second control command value can bereferred to as a PID command value.

The first control command value is obtained by adding a correction valueLIi to the second control command value PIDIi. The correction value LIiis created based on a difference LΔei between an absolute value |Δei| ofthe deviation in the control-target brake system i and an absolute value|Δej| of the deviation in the comparison-target brake system j, LΔei(n)(=|Δei(n)|−|Δej(n−1)|); a derivative value dLΔei of the difference,dLΔei(n)(=LΔei (n)−LΔei(n−1)); and an integral value |LΔei of thedifference, |LΔei(n)(=LΔei(n)+|LΔei (n−1)), according to an equationLIi=LKP (LΔei+LCP)+LKD (dLΔei+LCD)+LKI (|LΔei+LCI). Each of LKP, LKD,and LKI is a gain, and each of LCP, LCD, and LCI is a constant.

A first control command value Ii is obtained according to an equation,Ii=PIDIi+LIi. In the flowchart in FIGS. 4A and 4B, a deviation Δe isindicated as “error”, LΔe is indicated as “L_error”, and a difference inthe target value is indicated as “diff_Prefi,j”.

When the difference LΔei(n) in the absolute value of the deviation is apositive value, and the absolute value |Δei(n)| of the deviation in thecontrol-target brake system i is larger than the absolute value |Δej(n)|of the deviation in the comparison-target brake system j, a controldelay in the control-target brake system i is larger than a controldelay in the comparison-target brake system j, regardless of whether thepressure increasing control is being performed or the pressuredecreasing control is being performed.

A difference in control delay (the difference in response) when theabsolute value |LΔei(n)| is large is larger than the difference incontrol delay when the absolute value |LΔei(n)| is small.

Accordingly, when the difference LΔei(n) in the absolute value of thedeviation is a positive value, the correction value LIi is a positivevalue. The absolute value of the correction value LIi when the absolutevalue |LΔei(n) | is large is larger than the absolute value of thecorrection value LIi when the absolute value |LΔei(n) | is small. As aresult, the control command value for the control-target brake system iis set to a larger value (the first control command value is made largerthan the second control command value), and an electric current suppliedto each of the pressure increasing linear valves 80 and 81 and thepressure decreasing linear valves 90 and 91 is increased. The openingamount of each of the pressure increasing linear valves 80 and 81 andthe pressure decreasing linear valves 90 and 91 is increased, and alarger amount of hydraulic fluid is permitted to flow therethough.Regardless of whether the hydraulic pressure of the brake cylinder isincreased or decreased, the rate of change in the hydraulic pressure ofthe brake cylinder can be made higher, and the target value can bereached more promptly.

On the other hand, when the difference LΔei(n) in the absolute value ofthe deviation is a negative value, the control in the control-targetbrake system i is more advanced than the control in thecomparison-target brake system j, regardless of whether the pressureincreasing control is being performed or the pressure decreasing controlis being performed. The difference in response when the absolute value|LΔei(n) | of the difference in the absolute value of the deviation islarge is larger than the difference in response when the absolute value|LΔei(n) | is small. Accordingly, when the difference LΔei(n) in theabsolute value of the deviation is a negative value, the correctionvalue LIi is a negative value. The absolute value of the correctionvalue LIi when the absolute value |LΔei(n) | is large is larger than theabsolute value of the correction value LIi when the absolute value|LΔei(n) | is small. As a result, the control command value for thecontrol-target brake system i is set to a smaller value, and an electriccurrent supplied to each of the pressure increasing linear valves 80 and81 and the pressure decreasing linear valves 90 and 91 is decreased. Theopening amount of each of the pressure increasing linear valves 80 and81 and the pressure decreasing linear valves 90 and 91 is decreased, andthe amount of fluid flowing therethrough is limited. The limited amountof hydraulic fluid is permitted to flow through each of the pressureincreasing linear valves 80 and 81 and the pressure decreasing linearvalves 90 and 91. The rate of change in the hydraulic pressure of thebrake cylinder is suppressed, and the difference in response between thecontrol-target brake system i and the comparison-target brake system jcan be reduced. In this case, in the comparison-target brake system j,the rate of change in the hydraulic pressure of the brake cylinder isincreased by increasing the supply electric current.

The control command value creating program shown in the flowchart inFIGS. 4A and 4B is performed at predetermined time intervals.

In step S1, the target value and the actual value of the hydraulicpressure of the brake cylinder in the control-target brake system i, andthe target value and the actual value of the hydraulic pressure of thebrake cylinder in the comparison-target brake system j are obtained. Instep S2, the deviation Δei of the actual value from the target value inthe control-target brake system i, and the deviation Δej of the actualvalue from the target value in the comparison-target brake system j areobtained. In step S3, the control mode in the control-target brakesystem i and the control mode in the comparison-target brake system jare set based on the deviation Δei and the deviation Δej, respectively.In step S4, the difference in the target value Pref between thecontrol-target brake system i and the comparison-target brake system j(Prefi−Prefj) is obtained. In step S5, whether the absolute value of thedifference is equal to or smaller than a set value S is determined. Instep S6, it is determined whether the combination (MODEi, MODEj) of thecontrol mode in the control-target brake system i and the control modein the comparison-target brake system j is a predetermined combination.In other words, it is determined whether the combination of the controlmode in the control-target brake system i and the control mode in theother brake system j (MODEi, MODEj) is the combination of (pressureincreasing mode and pressure increasing mode) or the combination of(pressure decreasing mode and pressure decreasing mode).

When the absolute value of the difference in the target value(|Prefi−Prefj|) is equal to or smaller than the set value S, and thecombination of the control modes is the predetermined combination, thefirst control command value is created in step S7 to step S9. Thedifference LΔei(n) of the deviation is obtained by subtracting theabsolute value of the deviation in the comparison-target brake system jfrom the absolute value of the deviation in the control-target brakesystem i. Also, the derivative value dLΔei(n) and the integral value|LΔei(n) of the difference in the absolute value of the deviation areobtained. The control correction value LIi is obtained based on thedifference LΔei(n), the derivative value dLΔei (n), and the integralvalue |LΔei(n). The first control command value Ii is set to the sum ofthe second control command value PIDIi (PID control command value) andthe correction value LIi.

On the other hand, when the absolute value (|Prefi−Prefj|) of thedifference in the target value between the control-target brake system iand the comparison-target brake system j is larger than the set value S,or when the absolute value (|Prefi−Prefj|) of the difference in thetarget value is equal to or smaller than the set value S and thecombination of the control modes is not the predetermined combination,the second control command value (PID control command value) is createdin step S10.

The thus created control command value is output, the pressureincreasing linear valves 80 and 81 and the pressure decreasing linearvalves 90 and 91 are controlled based on the control command value,whereby the hydraulic pressure of the brake cylinder is controlled.

For example, when the braking operation is performed normally, theabsolute value of the difference in the target value of the hydraulicpressure between the brake cylinder for the right wheel and the brakecylinder for the left wheel is usually small. Accordingly, the firstcontrol command value is selected for each of the brake systems 230 and231 in many cases. In the case where the control mode is set to thepressure increasing mode in each of both the brake system i and thebrake system j, or in the case where the control mode is set to thepressure decreasing mode in each of both the brake system i and thebrake system j, if the control delay in the control-target brake systemi is larger than the control delay in the comparison-target brake systemj, the control command value is increased. A large amount of hydraulicfluid is permitted to flow through each of the pressure increasinglinear valves 80 and 81 and the pressure decreasing linear valves 90 and91, and the rate of change in the hydraulic pressure of the brakecylinder can be increased. Also, when the control in the control-targetbrake system i is more advanced than the control in thecomparison-target brake system j, the control command value isdecreased. Accordingly, the amount of hydraulic fluid flowing througheach of the pressure increasing linear valves 80 and 81 and the pressuredecreasing linear valves 90 and 91 is further limited. Therefore, therate of change in the hydraulic pressure of the brake cylinder can bereduced. Thus, the hydraulic pressures of the brake cylinders for theright and left front wheels can be changed at the same level ofresponse, and running stability of the vehicle can be improved.

In the case where the control-target brake system is the brake system230 for the left front wheel, when the first control command value isselected in the brake system 230 for the left front wheel and the firstcontrol command value is made larger, the second control command valuein the control-target brake system 231 for the right front wheel is madesmaller. In this case, the control command value is increased in one ofthe brake system 230 for the left front wheel and the brake system 231for the right front wheel, and the control command value is decreased inthe other of the brake system 230 and the brake system 231. Then, thegains LKP, LKD, and LKI, and the constants CP, LCD, and LCI, and thelike which are used to create the correction value LIi are set such thatthe levels of response in the brake systems 230 and 231 becomessubstantially the same.

Also, while the vehicle stability control is performed during thebraking operation, the target values of the hydraulic pressures of thebrake cylinders for the right and left wheels are not always the same.Also, the control mode in the brake system 230 and the control mode inthe brake system 231 are not always the same. In each of the brakesystems 230 and 231, the second control command value is usuallyselected, and the hydraulic pressures of the brake cylinders for therespective wheels are controlled independently of each other such thatthe braking slip becomes appropriate. The state similar to thatdescribed so far is realized during the anti-lock control as well.

As described so far, in the embodiment, it is possible to appropriatelyselect the control command value from among the first control commandvalue and the second control command value, based on whether theabsolute value of the difference in the target value of the hydraulicpressure of the brake cylinder between the control-target brake systemand the comparison-target brake system j is equal to or smaller than theset value, and based on whether the combination of the control modes isthe predetermined combination. The first control command value can becreated, when the levels of response actually need to be the same. Also,the second control command value is selected, when it is preferable notto take the information concerning the comparison-target brake system jinto consideration. Accordingly, the hydraulic pressure of the brakecylinder can be controlled based on the information concerning thecontrol-target the brake system i.

FIG. 6 is a block diagram showing the embodiment. In each of the brakesystem i for the left front wheel and the brake system j for the rightfront wheel, a consideration creating portion 250 is formed of a portionof the brake ECU 200, which stores steps S7 to S9 of the control commandvalue creating program shown in the flowchart in FIGS. 4A and 4B, aportion of the brake ECU 200, which performs steps S7 to 9, and thelike; and a non-consideration creating portion 252 is formed of aportion of the brake ECU 200, which stores step S10 shown in FIGS. 4Aand 4B, a portion of the brake ECU 200, which performs step S10, and thelike. Also, a control command value selecting portion 254 is formed of aportion of the brake ECU 250, which stores steps S5 and S6, a portion ofthe brake ECU 250, which performs steps S5 and S6, and the like.

Also, the brake ECU 200 and the like are the hydraulic brake apparatusesserving as the braking torque control devices.

In the above-mentioned embodiment, two control command value creatingportions are selected. However, two control command values may becreated, and then one of the two control command value may be selected.In either of these cases, one of the two created control command valuesis selected as the control command value to be output.

In the above-mentioned embodiment, when each of both the control mode inthe control-target brake system i and the control mode in thecomparison-target brake system j is the pressure increasing mode or wheneach of both the control mode in the control-target brake system i andthe control mode in the comparison-target brake system j is the pressuredecreasing mode, the first control command value is selected. However,even when the control mode in the control-target brake system i is thepressure increasing mode or the pressure decreasing mode, and thecontrol mode in the comparison-target brake system j is the maintainingmode, the first control command value may be created.

Also, the control command value may be created according to a controlcommand value creating program shown in a flowchart in FIG. 7.

In the embodiment, the control gains KP, KD, and KI are set based on adifference LLΔei in the deviation between the control-target brakesystem i and the comparison-target brake system j, the absolute value|Prefi−Prefj| of the difference in the target value Pref, and thecombination of the control modes (MODEi, MODEj). A difference LLΔe inthe deviation is indicated as LL_error in FIG. 7.

As described above, in the embodiment, gain correction values α, β, andγ are based on the difference LLΔei(=Δei−Δej) between the deviation Δeiand the deviation Δej, not based on the difference between the absolutevalue |Δei| of the deviation in the control-target brake system i andthe absolute value |Δej| of the deviation in the comparison-target brakesystem j. In the embodiment, the deviation Δe becomes a positive valuewhen the pressure increasing mode is set, and the deviation Δe becomes anegative value when the pressure decreasing mode is set. Accordingly,the gain correction values α, β, and γ that are used in the case wherethe pressure increasing mode is set, and the gain correction values α,β, and γ that are used in the case where the pressure decreasing mode isset are obtained independently of each other.

As in the above-mentioned embodiment, the gain correction values thatare used in the case where the pressure increasing mode is set, and thegain correction values that are used in the case where the pressuredecreasing mode is set may be obtained independently of each other,based on the difference LΔei in the absolute value of the deviation.

When the control gains KP, KD, and KI are αKP, βKD, and γKI,respectively (KP=αKP, KD=βKD, and KI=γKI), the proportional item gaincorrection value α, the derivative item gain correction value β, and theintegral item gain correction value γ are set according to a gaincorrection value setting routine and according to the followingrespective equations, α=f (Δei−Δej, Prefi−Prefj, MODEi, MODEj),β=g(Δei−Δej, Prefi−Prefj, MODEi, MODE), and γ=h(Δei−Δej, Prefi−Prefj,MODEi, MODE).

In step S51 in a flowchart in FIG. 8, it is determined whether theabsolute value |Prefi−Prefj| of the difference in the target valuebetween the control-target brake system i and the comparison brakesystem j is equal to or smaller than a threshold value Th. If theabsolute value is larger than the threshold value Th, the proportionalitem gain correction value α is set to “1” in step S52. When theproportional item gain correction value α is “1”, correction is notperformed, that is, the second control command value is selected(created).

When the absolute value is equal to or smaller than the threshold valueTh, the combination of the control mode MODEi in the control-targetbrake system i and the control mode MODEj in the comparison-target brakesystem j is obtained in steps S53 to S56. In steps S53 and S54, whetherthe control mode MODEi in the control-target brake system i is thepressure increasing mode or the pressure decreasing mode is determined.In steps S55 and S56, whether the control mode MODEj in thecomparison-target brake system j is the pressure increasing mode or thepressure decreasing mode is determined. When the control mode MODEi inthe control-target brake system i is the maintaining mode, or when thecontrol mode MIDEi in the control-target brake system i do not match thecontrol mode MODEj in the comparison-target brake system j, theproportional item gain correction value α is set to “1” in step S52.

Also, when each of both the control mode in the control-target brakesystem i and the control mode in the comparison-target brake system j isthe pressure increasing mode, the proportional gain correction value αis set in steps S57 and S58. When each of both the control mode in thecontrol-target brake system i and the control mode in thecomparison-target brake system j is the pressure decreasing mode, theproportional item gain correction value α is set in steps S59 and S60.

In steps S57 and S58, the proportional item gain correction value α istentatively set according to an equation, α=1+APKα×LLΔeij. Here, APKα isa constant. Also, LLΔei is the difference (Δei−Δej) between thedeviation Δei in the control-target brake system i and the deviation Δejin the comparison-target brake system j. Accordingly, in the case wherethe difference LLΔei in the deviation is a positive value, as theabsolute value thereof increases (as the control delay in thecontrol-target brake system i becomes larger than the control delay inthe comparison-target brake system j during the pressure increasingcontrol), the proportional item gain correction value α increases.

Finally, the proportional item gain correction value α is set accordingto an equation, α=MED (APαMIN, α, APαMAX). APαMIN is the minimum value,and APαMAX is the maximum value, and APαMIN and APαMAX are set inadvance. Since the proportional item gain correction value α is limitedso as to exceed neither the minimum value APαMIN nor the maximum valueAPαMAX, the proportional item gain correction value α is prevented frombeing excessively small or excessively large.

Thus, the proportional gain correction value α when the differenceLLΔeij in the deviation between the control-target brake system i andthe comparison-target brake system j is large becomes larger than theproportional gain correction value α when the difference LLΔeij issmall.

In steps S59 and S60 as well, the proportional gain correction value αis tentatively set according to an equation, α=1−REKα×LLΔei. REKα is aconstant. During the pressure decreasing control, the deviation Δei inthe control-target brake system i and the deviation Δej in thecomparison-target brake system j become negative values. Accordingly, inthe case where the difference LLΔei in the deviation is a negativevalue, as the absolute value of the difference LLΔei increases, thecontrol delay in the control-target brake system i becomes larger thanthe control delay in the comparison-target brake system j. Therefore,when the difference LLΔei in the deviation is a negative value theproportional gain correction value α is a positive value, and, ingeneral, as the absolute value of the difference LLΔei increases, theproportional gain correction value α increases. The proportional itemgain correction value α is set according to an equation, α=MED (REαMIN,α, REαMAX). REαMIN and REαMAX are limit values.

The derivative item gain correction value β and the integral item gaincorrection value γ are set in the same manner.

The control command value is created by using the control gains KP, KD,and KI that are corrected by the gain correction values α, β, and γ,respectively. The control command value is created according to thecontrol command value creating program shown in a flowchart in FIG. 7.

In the control command value creating program, as in the case of theabove-mentioned embodiment, the deviation Δei in the control-targetbrake system i and the deviation Δej in the comparison-target brakesystem j are obtained, and the control mode in the control-target brakesystem i and the control mode in the comparison-target brake system jare obtained. Then, the difference in the target value is obtained.

Then, in step S71, the difference LLΔe in the deviation between thecontrol-target brake system i and the comparison-target brake system jis obtained. In step S72, the gain correction values α, β, and γ areobtained according to the gain correction value setting routine. In stepS73, the control gains αKP, βKD, and γKI are set. In step S74, thecontrol command value is created. In a case where each of the gaincorrection values α, β, and γ is “1”, the second control command value(non-consideration control command value) is created. In the othercases, the first control command value (consideration control commandvalue) is created.

As described so far, in the embodiment, when the absolute value of thedifference in the target value between the control-target brake system iand the comparison-target brake system j is small, and the combinationof the control modes is the predetermined combination, the gaincorrection values α, β, and γ are set to values corresponding to thedifference in response. On the other hand, when the absolute value ofthe difference in the target value is large, or when the combination ofthe control modes is not the predetermined combination, each of the gaincorrection values α, β, and γ is set to “1”. As a result, when theinformation concerning the comparison-target brake system needs to betaken into consideration, the first control command value is created. Onthe other hand, when the information concerning the comparison-targetbrake system need not be taken into consideration, the second controlcommand value is created. Also, at the first control command value, asthe difference in the response increases, each of the gain correctionvalues α, β, and γ is set to a value which is deviated from “1” by alarger amount. Accordingly, if the control command value created byusing the gain correction value is output, the difference in theresponse can be reduced.

In the above-mentioned embodiment, the description has been madeconcerning the case where feedback control is performed, and the controlcommand value is created based on the deviation of the actual value fromthe target value. However, the invention can be applied to the casewhere the control including the feed-forward control and the feedbackcontrol is performed. When the sum of the control command value set bythe feed-forward control and the control command value set by thefeedback control is used as the control command value, the invention canbe applied to the control command value set by the feedback control.

Also, the invention can be applied to the case where the feed-forwardcontrol is performed. The value obtained by correcting the secondcontrol command value, which is created based on the target value in thecontrol-target brake system, based on the difference between the actualvalue in the control-target brake system and the actual value the otherbrake system is used as the first control command value. When theabsolute value of the difference in the target value is small, when thecombination of the control modes is not the predetermined combination,and the like, the first control command value is selected.

When each of the control mode in the control-target brake system and thecontrol mode in the comparison-target brake system is the pressureincreasing mode, or when each of the control mode in the control-targetbrake system and the control mode in the comparison-target brake systemis the pressure decreasing mode, that is, when the control mode in thecontrol-target brake system matches the control mode in thecomparison-target brake system, the first control command value may beselected even if the absolute value of the difference in the targetvalue is large. When these control modes are the same, the directions inwhich the braking torque changes are also the same. Accordingly, it maybe preferable to make the levels of response equal to each other, evenwhen the target values are different from each other.

Also, the invention can be applied to each of the case where the frontand rear wheels on the right side are controlled together with eachother and the case where the front and rear wheels on the left side arecontrolled together with each other. In each of these cases, theindividual hydraulic control devices 70 and 72 are controlled togetherwith each other, and the individual hydraulic control devices 71 and 73are controlled together with each other.

In the above-mentioned embodiment, the first control command value orthe second control command value is selected based on, as at least oneof parameters, the absolute value of the difference between the targetvalue of braking torque in the control-target brake system and thetarget value of braking torque in the other brake system, in step 5 inFIG. 4 or step 51 in FIG. 8 However, Instead of the parameter, the firstcontrol command value or the second control command value may beselected based on, as at least one of parameters, an absolute value of adifference between an absolute value of a deviation of an actual valuefrom the target value of the braking torque in the control-target brakesystem, and an absolute value of a deviation of an actual value from thetarget value of the braking torque in the other brake system.

In the above-mentioned embodiment, the description has been madeconcerning the case where the control command values are created for thebrake system 230 for the left front wheel and the brake system 231 forthe right front wheel. However, the invention can be applied to the casewhere the control command values are created for the brake system 232for the left rear wheel and the brake system 233 for the right rearwheel. In this case, the pressure decreasing linear valves 92 and 93 arenormally open valves. The rate of decrease in the hydraulic pressure ineach of the brake cylinders 22 and 23 when the control command valuethat is the supply electric current is large is lower than that when thecontrol command value is small. Accordingly, during the pressuredecreasing control, the control command value, which is used when thecontrol delay in the control-target brake system i is larger than thecontrol delay in the comparison-target brake system j, is made smallerthan the control command value, which is used when the control delay inthe control-target brake system i is smaller than the control delay inthe comparison-target brake system j.

In the above-mentioned embodiment, the description has been madeconcerning the case where the number of the comparison-target brakesystem is one. However, the number of the comparison-target brakesystems may be two or three. When the number of the comparison-targetbrake systems is two or more, for example, the first control commandvalue may be created by obtaining the correction values for therespective comparison-target brake systems, and employing the averagevalue of the plural correction values. Also, instead of the averagevalue, the intermediate value, the maximum value or the minimum valuemay be employed. The gain correction value may be obtained in the samemanner. In addition, when the information concerning the plural brakesystems is taken into consideration, the first control command value maybe selected, only when all the control modes in the plural brake systemsare the same control mode.

For example, when the brake system 230 for the left front wheel is thecontrol-target brake system, it is determined whether the absolute valueof the difference in the target value between the brake system 230 forthe left front wheel, and each of the brake system 231 for the rightfront wheel, the brake system 232 for the left rear wheel, and the brakesystem 233 for the right rear wheel is equal to or larger than the setvalue, and it is determined whether the combination of the control modein the brake system 230, and the control mode in each of the brakesystem 231 for the right front wheel, the brake system 232 for the leftrear wheel, and the brake system 233 for the right rear wheel is thepredetermined combination. Based on the results of these determinations,whether the information concerning the comparison-target brake systemsis taken into consideration is determined. In this case, during normalbraking operation, when the target value of the hydraulic braking torqueof the front wheel and the target value of the hydraulic braking torqueof the rear wheel are set to the same value, even if thecomparison-target brake systems are the brake systems 232 and 233 forthe rear wheels, the first control command may be selected due to therelationship. Also, during the normal braking operation, for example,when the target values of the hydraulic braking torque of the respectivewheels are set based on loads applied to the respective wheels inaddition to the braking torque required by the driver, when the targetvalues of the hydraulic braking torque of the respective wheels are setsuch that the slip states of the wheels become the same state, and thelike, the target value of the hydraulic pressure of the brake cylindermay vary with each brake system for the wheel. In this case, the secondcontrol command value is selected in some cases, and the first controlis selected in the other cases, depending on the relationship with thecomparison-target brake systems. Since the second control command valueis selected when the absolute value of the difference in the targetvalue is large, in the control-target brake system 230, the hydraulicpressure of the brake cylinder can be controlled based on the state ofthe control-target brake system 230, without taking the states of theother brake systems 231, 232 and 233 into consideration.

In the above-mentioned embodiment, the description has been madeconcerning the case where the invention is applied to the hydraulicbrake apparatus. However, the invention can be applied to an electricbrake apparatus.

Each of the brake systems may include one brake and one controlactuator, may include plural brakes and plural control actuators, or mayinclude plural brakes and one control actuator. In any one of thesecases, in one brake system, the one or more control actuators arecontrolled together with each other, and the one or more brakes areoperated together with each other.

The brake may be a hydraulic brake that is operated by the hydraulicpressure of the brake cylinder, or may be the electric brake that isoperated by driving force (pressing force) of the electric motor. Thecontrol actuator may include the electromagnetic control valve, or mayinclude the electric motor control circuit.

The consideration creating portion my create the control command valuein consideration of the information concerning one brake system that isdifferent from the control-target brake system, or may create thecontrol command value in consideration of the information concerning twoor more brake systems.

The information concerning the operation of the at least one brake inthe brake system is the information indicating the operating state ofthe brake. For example, the information corresponds to at least one ofthe information indicating the actual operating state, the informationindicating the target operating state, the information concerning thedeviation of the actual operating state from the target operating state,and the like. Since the operating state of the brake corresponds to theoperating state of the control actuator, the information concerning theoperation of the control actuator (the information concerning thecontrol) can be included in the information concerning the operation ofthe brake.

More specifically, the information corresponds to at least one of thetarget value of the braking torque of the brake (for example, the targetvalue of the hydraulic pressure of the brake cylinder when the brake isthe hydraulic brake, or the target value of the pressing force of theelectric motor when the brake is the electric brake), the actual valueof the braking torque, the deviation of the actual value from the targetvalue of the braking torque, the control command value for the controlactuator, and the like. The information that is taken into considerationwhen the control command value is created may include at least one ofthe target value of the braking torque of the brake, the actual value ofthe braking torque, the deviation of the actual value from the targetvalue of the braking torque, the control command value for the controlactuator, and the like.

The braking torque control device may perform feedback control, or mayperform feed-forward control. When control including the feedbackcontrol and the feed-forward control is performed, the invention can beapplied to at least one of the control command value created by thefeedback control and the control command value created by thefeed-forward control.

While the invention has been described in detail with reference to thepreferred embodiments, it will be apparent to those who are skilled inthe art that the invention is not limited to the above-mentionedembodiments, and that the invention may be realized in various otherembodiments within the scope of the invention.

1. A brake system control apparatus comprising: plural brake systems,each brake system including at least one brake and a control actuatorthat can control braking torque generated by the at least one brake, anda braking torque control device that creates a control command value forthe control actuator of each of the brake systems, and that outputs thecreated control command value to the control actuator, wherein thebraking torque control device comprises: a consideration commandcreating portion that creates a first control command value for thecontrol actuator of a control-target brake system, which is one of theplural brake systems, based on information concerning an operation of atleast one brake in the control-target brake system, and informationconcerning an operation of at least one brake in at least one of theother brake systems; a non-consideration command creating portion thatcreates a second control command value for the control actuator of thecontrol-target brake system based on the information concerning thecontrol-target brake system, the second control command being not basedon the information concerning the at least one of the other brakesystems; and a control command value selecting portion that selects oneof the first control command value created by the consideration commandcreating portion and the second control command value created by thenon-consideration command creating portion, based on at least one of (a)an absolute value of a difference between a target value of brakingtorque in the control-target brake system and a target value of brakingtorque in the at least one of the other brake systems; and (b) acombination of a control mode in the control-target brake system, whichis set to one of a pressure increasing mode, a pressure decreasing modeand a pressure maintain mode, and a control mode in the at least one ofthe other brake systems, which is set to at least one of a pressureincreasing mode, a pressure decreasing mode and a pressure maintainingmode, the selecting portion selects the first control command valuecreated by the consideration command creating portion when the controlmode in the control-target brake system and the control mode in the atleast one of the other brake systems are the same, and both the controlmode in the control-target brake system and the control mode in the atleast one of the other brake systems is the increasing mode in which thebraking torque is increased or the decreasing mode in which the brakingtorque is decreased; and the selecting portion selects the secondcontrol command value created by the non-consideration command creatingportion when one of the control mode in the control-target brake systemand the control mode in the at least one of the other brake systems isthe increasing mode in which the braking torque is increased, and theother of the control mode in the control-target brake system and thecontrol mode in the at least one of the other brake systems is thedecreasing mode in which the braking torque is decreased.
 2. The brakesystem control apparatus according to claim 1, wherein the considerationcommand creating portion creates the first control command value basedon the target value and an actual value of the braking torque in thecontrol-target brake system, and the target value and an actual value ofthe braking torque in the at least one of the other brake systems. 3.The brake system control apparatus according to claim 2, wherein theconsideration command creating portion creates the first control commandvalue based on a deviation of the actual value from the target value ofthe braking torque in the control-target brake system, and the deviationof the actual value from the target value of the braking torque in theat least one of the other brake systems.
 4. The brake system controlapparatus according to claim 1, wherein the consideration commandcreating portion corrects the second control command value created bythe non-consideration command creating portion, based on the targetvalue and an actual value in the at least one of the other brake systemsand the target value and an actual value in the control-target brakesystem.
 5. The brake system control apparatus according to claim 4,wherein the consideration command creating portion creates the firstcontrol command value by correcting the second control command valuecreated by the non-consideration command creating portion, based on adeviation of the actual value from the target value of the brakingtorque in the control-target brake system and a deviation of the actualvalue from the target value of the braking torque in the at least one ofthe other brake systems.
 6. The brake system control apparatus accordingto claim 5, wherein the consideration command creating portion sets acorrection value based on a difference between an absolute value of thedeviation of the actual value from the target value of the brakingtorque in the control-target brake system, and an absolute value of thedeviation of the actual value from the target value of the brakingtorque in the at least one of the other brake systems.
 7. The brakesystem control apparatus according to claim 4, wherein the considerationcommand creating portion creates the first control command value for thecontrol-target brake system based on the information concerning thecontrol-target brake system and information concerning a brake systemwhose level of response is required to be the same as a level ofresponse of the control-target brake system.
 8. The brake system controlapparatus according to claim 1, wherein the consideration commandcreating portion creates the first control command value based on theinformation concerning the control-target brake system and informationconcerning a brake system including the brake that suppresses rotationof a wheel which is on an opposite side, in a right-and-left direction,of a wheel whose rotation is suppressed by the control-target brakesystem.
 9. The brake system control apparatus according to claim 1,wherein each brake system includes a brake that is a hydraulic brakethat applies hydraulic braking torque to a brake rotational body thatcan rotate together with a wheel by pressing a friction member to thebrake rotational body due to hydraulic pressure of a brake cylinder,thereby suppressing rotation of the wheel; the control actuator includesat least one electromagnetic control valve that can control thehydraulic pressure of at least one brake cylinder; and the brakingtorque control device controls the hydraulic pressure of the at leastone brake cylinder by creating the control command value correspondingto an electric current supplied to the electromagnetic control valve,and outputting the control command value to the electromagnetic controlvalve.
 10. The brake system control apparatus according to claim 9,wherein the electromagnetic control valve permits hydraulic fluid toflow through the electromagnetic control valve at an opening amount thatis decided based on at least the electric current supplied to theelectromagnetic control valve; and the consideration command creatingportion creates the first control command value indicating the electriccurrent supplied to the electromagnetic control valve such that adifference in response between the control-target brake system and theat least one of the other brake systems is reduced.
 11. The brake systemcontrol apparatus according to claim 10, wherein the electromagneticcontrol valve includes a seating valve including a valve element, avalve seat, and a spring; and a solenoid.